AK4671_10 Datasheet, PDF (65/166 Pages) Asahi Kasei Microsystems – Stereo CODEC with MIC/RCV/HP-AMP

[AK4671]
(4) Gain Compensation (EQ0)
Gain Compensation is used to compensate the frequency response and the gain that is changed by Stereo Separation
Emphasis Filter. Gain Compensation is composed with Equalizer (EQ0) and the Gain (0dB/+12dB/+24dB). E0A15-0,
E0B13-0 and E0C15-0 bits set the coefficient of EQ0. GN1-0 bits set the gain (Table 23). EQ0 bit controls ON/OFF of
EQ0. When EQ is OFF and the gain is 0dB, the audio data passes this block by 0dB gain. The coefficient should be set
when EQ0 bit = “0” or PMADL=PMADR=PMDAL=PMDAR bits = “0”.
fs: Sampling frequency
fc₁: Pole frequency
fc₂: Zero-point frequency
K: Filter gain [dB] (Maximum +12dB)
Register setting (Note 61)
E0A[15:0] bits =A, E0B[13:0] bits =B, E0C[15:0] bits =C
(MSB=E0A15, E0B13, E0C15; LSB=E0A0, E0B0, E0C0)
1 + 1 / tan (πfc₂/fs)
A = 10^K/20 x
,
1 + 1 / tan (πfc₁/fs)
1 − 1 / tan (πfc₁/fs)
B=
,
1 + 1 / tan (πfc₁/fs)
1 − 1 / tan (πfc₂/fs)
C =10^K/20 x
1 + 1 / tan (πfc₁/fs)
Transfer function
H(z) =
A + Cz ^−1
1 + Bz ^−1
Gain[dB]
K
fc₁
fc₂
Frequency
Figure 61. EQ0 Frequency Response
GN1
GN0
Gain
0
0
0dB
(default)
0
1
+12dB
1
x
+24dB
Table 23. Gain select of gain block (x: Don’t care)
MS0666-E-02
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2010/06